1. Field of the Invention
The invention relates to a polarized light irradiation device for purposes of optical alignment of liquid crystals by irradiation of an alignment layer of a liquid crystal cell element with polarized light.
2. Description of Related Art
A liquid crystal cell element usually consists of two substrates. On one of these substrates a driver system for triggering a liquid crystal (for example, a thin film transistor), electrodes for triggering the liquid crystals which are formed of transparent conductive films, and an alignment layer or the like for alignment of the liquid crystals in a certain direction are formed. On the other of these substrates, a light screening film is formed which is called a black matrix. In a color liquid crystal cell element, a color filter, electrodes for triggering the liquid crystal, and an alignment layer are formed.
The alignment layer is usually produced by subjecting the surface of a thin layer, such as polyimide resin or the like, to treatment which is called rubbing, and by providing it with fine grooves in a certain direction; this is designed to align the molecules of the liquid crystal along these grooves in a certain direction. In this rubbing treatment, a process is commonly used in which the alignment layer is produced by rubbing the substrate with a cloth, which is called the rubbing cloth, and with which a turning roller is wound.
Rubbing formation of the alignment layer is done by rubbing the substrate with a rubbing cloth. In doing so, occurrence of adverse effects such as dust, static electricity, scratches and the like and a decrease of yield cannot therefore be prevented.
Recently, therefore, a technique was proposed in which alignment of the liquid crystals is produced without the alignment layer being subjected to the above described rubbing (the technique of aligning the liquid crystal without rubbing is hereinafter called "nonrubbing").
The nonrubbing technique is a process using polarized light. In this process, the following is performed.
1) The thin layer, as the alignment layer, such as a polyimide resin or the like, is irradiated with polarized light. The polymer of the thin layer is subjected to polarization and a structural change produced only in a certain direction by a photochemical reaction.
2) In this way, alignment of the molecules of the liquid crystal on the thin layer is produced (hereinafter, this alignment technique is called the "optical alignment technique").
In this process, UV radiation (ultraviolet radiation) with high energy is often used as the emitted polarized light. Recently, an alignment layer material has also been developed in which polarization or structural change is produced by visible radiation.
FIG. 12 shows, in schematic form, a known arrangement of an irradiation device which emits polarized light and executes optical alignment of the alignment layer of a liquid crystal cell element. The device of U.S. Pat. No. 5,934,780 possesses such an arrangement.
In the figure, an irradiation device 10 has a lamp 1 which emits light which contains UV radiation emitted which is focussed by an oval focusing mirror 2, reflected by a first planar mirror 3, and is incident on an integrator lens 4 (which may also be called a fly eye lens). The light emerging from the integrator lens 4 is incident via a shutter 5 and via a second planar mirror 6 on a collimation lens 7, which converts the light into parallel light, which is incident on a polarization element 8. The polarized light emerging from the polarization element 8 is incident on a workpiece W, such as a liquid crystal cell element or the like.
However, to produce a liquid crystal cell, a large surface is needed. On the outlet side of the collimation lens, therefore, the light flux spreads. Therefore, a gigantic polarization element is needed to obtain light polarized over the entire region to be irradiated.